looking at the Citadel colors, i would say that Mournfang Brown would make a nice base, and then add in Khorne Red to bring it up to that nice oxblood color...
i can't say what the painter's technique was for the shading, but i would do a basecoat, then layer up, leaving a bit of the base showing around the edges, and then give it a wash using some blue in the red, before carefully layering up the red again...
i use P3 Coal Black, Sanguine Base, and P3 Flesh Wash as my shading mix for reds...
you could use Incubi Darkness, Khorne Red, and Nuln Oil to approximate the mix...
i highly recommend Sanguine Base, Skorne Red, and Khador Red Base

...
the Skorne Red is better for this dark scheme, but KRB is my favorite bright red out there...
all three colors cover very well compared to others i've tried...
hope that helps...
cheers
jah